This invention relates to computing scales and more particularly to an improved computing scale which weighs an article and computes desired data from the article weight such as an article value based upon the article weight and a predetermined price per unit weight.
Computing scales are used in many industries for weighing articles and computing desired data from the article weight. Computing scales are, for example, commonly used in the retail food sales industry for weighing meats, produce and similar articles sold by weight and for computing from the article weight the value of such article based upon a predetermined price per unit weight. The article weight and the computed value are then displayed to the store clerk and to customers and, in some cases, are also automatically printed on an article label.
Computing scales are also used for obtaining data other than the value of articles. Such scales, for example, are sometimes used for obtaining a count of the number of pieces in a container. The scales weigh the number of pieces in the container and divide the measured weight by an average weight per piece for obtaining a pieces count. Or, computing scales may be used for obtaining a net weight of a material having a known percentage, by weight, of impurities. For example, if it is known that a particular material has a moisture content of 2% by weight, it may be desired to multiply the measured gross weight from a scale by 98% so that the net or dry weight of the material is indicated.
Computing scales have become very sophisticated and highly accurate with the development of digital computing techniques. Advance computing scales convert a measured gross article weight into a digital format, subsequently convert the digitized gross weight into a digital net weight, and multiply the net weight by a price per unit weight or some other factor in a digital computer. The result appearing at the computer output may then be displayed on a digital readout, such as on Nixie tube readouts or on seven-segment readout devices. In some instances, a record is also printed of the computer output. The record may, for example, consist of a label for application to the article being weighed.
The use of digital techniques and the greatly increased accuracy of modern digital computing scales has accentuated some problems which were generally of little concern in the relatively slow and less accurate prior art analog computing scales. One such problem area is jitter in the measured weight. As used herein, weight "jitter" refers to very small fluctuations or oscillations in the measured weight generally caused by small vibrations of either the article being weighed or the scale. Digital computing scales used for retail sales typically indicate weight to 1/100th of a pound. At this accuracy, a relatively small vibration may cause the indicated digital weight to jitter between two or more values. This problem is accentuated when an article has a weight between two values. If, for example, an article weighs 9.135 pounds and the scale indicates only to 1/100th of a pound, the displayed weight will tend to jitter or alternate between 9.13 pounds and 9.14 pounds. This in turn may cause data computed from the article weight to jitter between two values.
Computing scales are generally provided with means for supplying a tare weight to the computer for use in determining net weights. In many scales, a separate set of buttons or switches are used solely for tare weight entries. More sophisticated computing scales may measure the tare weight on the scale and automatically enter the measured tare weight when an "enter tare" switch is closed. These scales are often provided with a switch for selecting either an automatic mode or a manual mode for entering tare weights. However, the mode selecting switches and the manual tare entry keys are not always convenient and there is a possibility of entering an erroneous tare weight. Furthermore, when the scale is designed to compute values, a separate set of keys or switches has generally been required for entering price per unit weight data. This results in an unnecessary duplication of switches or keys for entering data into the computer.